1. Field of the Invention
The present invention relates to a method and apparatus for the sealing of packages, and particularly to a method and apparatus for sealing packages using continuous motion intermittent ultrasonic sealing technology.
2. Related Background Art
The prior art discloses commonly-used hot sealing and cold sealing technology to seal packages. For example, U.S. Pat. No. 6,319,184 B1 (DeMatteis et al.) describes a process for cold sealing two layers of plastic film material together. The bag formed by the DeMatteis invention has a closed bottom, a continuously closed periphery, and an open top. The bag is provided with a cold seal, which does not form a part of the closed bottom or continuous closed periphery of the bag. The first and second layers of the bag must be opposed to each other so that proper sealing of the two layers may occur. Compression dies are provided on at least one side of the juxtaposed first and second layers, and the compression dies are sized accordingly to provide the desired size and shape of the cold seal. Thereafter, the compression dies are impressed across the juxtaposed first and second layers at a temperature and pressure sufficient to fuse the first and second layers together. However, the compression dies are impressed at an insufficient temperature and pressure to permanently fuse the first and second layers so that the layers, when separated at the cold seal, retain their structural integrity. In DeMatteis et al., a hot seal is generally described as a seal that will not part because the two layers of plastic were sealed together under a temperature and pressure where the molecular structure of the two plastic layers was permanently bonded and fused together. Moreover, in DeMatteis et al., a cold seal is generally described as, in essence, an imperfect hot seal, where the cold seal occurs when an insufficient temperature or pressure is used to seal the two layers (see, e.g., the specification at col. 1, line 57 to col. 2, line 38).
The prior art also discloses commonly-used anvil and ultrasonic horn components that are used to seal packages. For example, U.S. Pat. No. 5,976,315 (Martin) describes a stationary anvil for an ultrasonic sealing unit for sealing at least two sections composed of a plastic coated material, where the ultrasonic sealing unit comprises a sonotrode movable relative to the anvil. In Martin, the anvil has an anvil body with a sealing surface at a front of the body. The sealing surface has raised and indented areas where the raised areas are configured as narrow ribs. One of the ribs is a lower retaining rib running along a free lower edge of the sealing surface. Another of the ribs is a central sealing rib, which is located above and parallel to the lower retaining rib, and extends across the entire width of the sealing surface.
U.S. Pat. No. 5,775,055 (Giacomelli et al.) describes an anvil system that includes a plurality of stationary anvils having an interconnected cooling system. Each of the anvils has a means for acoustically insulating the anvil body from ultrasonic energy which originates from an ultrasonic horn. The insulation means may be an airspace slot that essentially separates the vibrating portion of the anvil from the anvil body. In Giacomelli et al., the invention provides a seal, for example, on a gable-type closure, which is used, for example, on the top of milk cartons. Here, the top fin is captured between an ultrasonic sealing horn and an anvil, and ultrasonic energy is transduced from the horn to the joint, which causes the heat-sealable material in the fin to fuse, thereby forming a seal.
U.S. Pat. No. 4,767,492 (Fukusima et al.) describes an ultrasonic sealing apparatus where pairs of sheet-like members at a bottom portion of a tubular member are fuse-bonded together by frictional heat that is generated by ultrasonic vibration. The apparatus includes a horn (see, e.g., FIG. 3, reference numeral 1) and anvil (see, e.g., FIG. 3, reference numeral 2) that were interposed with the material to be fuse-bonded together. The horn and anvil provide contact surfaces (see, e.g., FIG. 3, reference numeral 3) in contact with the material to be fused. Each of the contact surfaces is formed with a plurality of grooves (see, e.g., FIG. 1B, reference numeral 4) to provide a plurality of protrusions (see, e.g., FIG. 1B, reference numeral 5). Each of the protrusions has a flat upper surface and slanted side surfaces (see, e.g., FIG. 1B, reference numeral 6), so that the protrusion has a trapezodial cross-section. The horn applies ultrasonic vibration to the fuse-bonding surfaces of the material to be fused in a direction parallel therewith in association with the anvil.
U.S. Pat. No. 4,517,790 (Kreager) describes an apparatus and method for the continuous rotary ultrasonic sealing of packages. The apparatus utilizes a rotary anvil and cutter knife and an ultrasonic horn that has an adjustable, simulated, rotary motion that moves in synchronism with the anvil for providing an end seal on packages.
U.S. Pat. No. 4,534,818 (Kreager et al.) describes an automatic form-and-fill packaging machine that is adapted to ultrasonically seal bags made from ultrasonically sealable flexible packaging material. A method to utilize the machine is also described. In Kreager et al., a packaging machine is provided with a first ultrasonic back seal forming unit that produces a continuous longitudinal back seal on the bag, and a second ultrasonic sealing unit, which is provided in a pair of jaw members and are adapted to form the end seals of the bag perpendicular to the direction of travel of the packaging material. The second ultrasonic sealing unit is provided with a horn and a stationary anvil in opposing jaw members, such that when the jaws are shut, the flexible packaging material is tensioned against the sealing areas to form the end seals.
The references discussed above do not disclose or suggest a method and apparatus capable of sealing packages using continuous motion intermittent ultrasonic sealing. Such a sealing method and apparatus would be highly desirable.
This invention is directed to a method and apparatus for the sealing of packages, and particularly a method and apparatus for sealing packages using continuous motion intermittent ultrasonic sealing technology.
It is therefore an object of the present invention to provide a new and useful method and apparatus for sealing packaging material using ultrasonic technology. The packaging material is supplied to an anvil and horn-sealing station. The anvil has a cam shape and, in a preferred embodiment, can be caused to rotate, respective to a horn, by an AC servo that has digital feedback capabilities to change the rotating speed of the anvil. In addition, the rate of rotation of the anvil can be changed based on the desired spacing by the user between seals and the horn. The horn, which is preferably stationary, provides an ultrasonic vibration to the packaging material. The packaging material is sealed between the anvil and the horn. The desired spacing between seals may be varied by adjusting the rate of anvil rotation and/or speed at which the packaging material passes between the anvil and horn. The packaging material may be provided continuously and passes between the horn and anvil at speeds in excess of 500 feet of packaging material per minute.